ToME WikiDescribe IdeaArchive/Items/Gemstone sloted weapons here.
BrianBenson:With the gems being the fuel source for many items now, maybe it'd make sense if other items could use them. For instance, if you had a boomerang of minor spells and threw it normaly, nothing would happen other than its base damage (is it small wooden, small metal, etc.) but if you zapped it, itd let you choose from a small selection of spells and use a gem to fuel it. So instead of throwing normaly, I could throw it with the effect of it causing light at the end of its path or collision, or it could cause an explosion killing a group of monsters, etc. Also, special lamps could be fueled by magic, or allow spells...demon swords could be fit with a cursed gem to be able to give itself temporary damage boosts and more powerful spells, you could have an armor of mana that consumes charges from your gems instead of your health points, etc.
DarkGod: In the latest alpha I have made some fun items like that. Like the dragon scale mail of glaurung which sometimes, if a gem is embedded, will trigger on spellcast to absord the spell cost on the gem mana instead of the player mana. We can think of many other such things 
Gems also can be special, the Arkenstone of Thrain is a dsouble usage item. It is a light source as we all know it, but it can also be used as a powerful gem to embed in other items. When such item tries to use the gem mana a light room effect may trigger from the gem special properties. So if you embed the arkenstone in the PDSM you get a chance to have a mana-free, light explosion, spell cast Nifty ? 
LordEstraven: Definitely. 
BTW, is this gem stuff supposed to replace the current alchemy system? It does look a lot better to me...
NeilStevens: The goal is NOT to create new items. Even if we DO allow you to create new items, you're not going to be able to create artifacts anyway! Artifacts are being tightened WAY up in ToME 3.
Zonk: That's a bit...similar to my own idea, though that actually means that it's good What I would suggest, though, is to be able to to make 'generic'effects for socketed gems instead of having to define the effects for every item like you did with the DSM. Might also be nice if there was a sorceror ability to 'extract'mana from gemstones, destroying them - so gemstones can act as mana batteries.
BrianBenson:Well, I was just hoping to see zapable items that don't take so many turns to reuse that they are useless in combat like in all the other bands. Also, if there were many items like these being very varied but rare, it would spice up the game...especialy if they weren't all so expensive you couldn't buy weak ones early on. How rare will gems be...and will certain items require gems of a certain quality or better to work or something?
NeilStevens: Weak gems should be about as common as wands are now. The best gems should be at least as rare as the best rods in ToME 2.